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The method of decoration with anthraquinone has been used to study the electrical structure of matching cleavage surfaces of CaF,, LiF, NaCl, MgO and mica single crystals on the scale of optical microscopy. It has been found that the crystallization images of anthraquinone on matching areas of cleavage surfaces are regularly interconnected. From these crystallization pictures the electrical structure of the matching a r e a has been determined. The matching areas of CaF, cleavages along (111) have identical charge signs; the LiF matching cleavage areas along (100) have either opposite charge signs or identical but differing in magnitude; the NaCl matching cleavage surfaces along (100) are mainly charged negatively, however, regions are also observed which differ either in charge sign or magnitude; the matching areas of MgO cleavage surfaces along (100) are either charged positively or display low electrical activity; the matching cleavages of mica along (001) contain mostly positively charged areas with electrical axes displaced by 120' with respect to one another, small areas which are charged negatively, and also regions of low electrical activity. Suggestion is made that on brittle fracture of crystals the precise cleavage planes are in many caaes attributed to the defect structure of crystals, to the presence of two-dimensional boundaries between areas of different electrical structure. Fracture of single crystals, however, can also occur statistically as a consequence of their ideal or highly generalized defect structure. The regular correspondence of crystallization pictures on the surface of local areas of matching cleavages lends further support t o the view that crystallization is a matrix replication process, programmed in the electrical structure of crystal substrates. 68G. I. DISTLER et al.

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